Rails Logger::Shifting Problem

I ve run my rails project by creating 3 instance using mongrel cluster

mongrel_rails cluster::configure -p 8000 -n 3

now my project running three consequent ports like 8000,8001,8002
ports
i am using rails version --->2.1.1

   on the first day no problem in creating logfilename.log for running
all 3 ports.

Problem is ,

on next day when application is running in 1st instance its creating a
backup of logfilename.log as file_previous_date.log when same rails
project running at the 2nd instance (port 8001) on the that day.

         The following error occurred ,

        Logger::ShiftingError in controller
        Shifting failed. closed stream

Could any one give a solution for this problem

Thanx in advance